Due to improved Internet infrastructures and the widespread of communication terminals, such as cellular phone terminals, personal computers, and VoIP (Voice over Internet Protocol) phone sets, the number of Internet users is now exploding. Under such circumstances, security problems such as computer viruses, hacking and spam mails have become apparent, requiring appropriate techniques for communication control. Also, since improved communication environments have enormously increased communication traffic, there are required communication control apparatuses that enable high-speed processing of a large volume of data.    [Patent Document 1] Japanese Patent Application Laid-open No. 4-180425.